Not applicable.
Not applicable.
The present invention relates to dispensers used in liquid holding tanks in which the liquid level changes, and in particular such dispensers which dispense cleanser into toilet tanks.
A variety of dispensers exist for automatically dispensing chemicals into a water tank. See for example U.S. Pat. Nos. 5,924,142; 5,903,930; 5,839,128; 5,718,261; D376,840; 5,551,095; 5,488,742; D365,138; 5,152,015; 5,090,443; 5,038,417; 4,915,260; 4,696,414; 4,663,786; 4,660,231; 4,534,071; 4,429,809; 4,346,483; 4,285,074; 4,189,793; 4,101,043; 3,913,151; 3,874,007; 3,778,850; 3,698,021; 2,587,388; and 1,602,554. See also GB 2,167,041; EP 1,026,331; and WO 99/08076. See also Ser. No. 10/142,708 filed May 10, 2002. The disclosure of these publications and applications are incorporated by reference as if fully set forth herein. A number of these automated dispenser systems use some type of float that follows the water level in the tank to control dispensing.
Many such conventional automatic dispensers have a tendency for the product that is being dispensed to leak out of the dispenser in a somewhat uncontrolled manner. This tendency can increase the longer the particular dispenser is used. This can result in overdosing of the product or the uncontrolled draining of the liquid into the bowl, and thus waste of cleaning compositions.
Leakage of this type can arise from improper sealing of the valve head against the valve seat, which can be caused by insufficient buoyant forces acting on the valve. An even more important cause of such leakage is that the sealing surfaces that control outflow become degraded over time due to prolonged exposure to the tank water or the cleanser. This is particularly of concern where one or more valve elements are made of rubber.
Even if non-rubber materials are substituted for the rubber in such valve seat and valve head applications, leakage can still occur. In this regard, some materials are too inflexible to consistently insure a non-leaking seal. Others, while being suitable for sealing when they are properly configured, tend to be too flexible (such that they are subject to non-resilient deformation during use).
Accordingly, there is still a need in the art for dispensers of this type having improved outlet valving parts (particularly valve heads) that are resistant to degradation in the environment of stringent cleaning chemicals, yet otherwise suitable for use.
In one aspect the invention provides a dispenser for dispensing a composition (for example a liquid toilet bowl cleaner) from a container in response to liquid level changes in a tank. The dispenser has a receiver (for example an upwardly open holster) suitable to receive the container and to dose composition received from the container to a valve seat defining a flow opening. The dispenser also has a valve for controlling outflow through the flow opening, the valve having a flexible head supported by an essentially trapped gas pocket. Typically, the valve will be linked to a float suitable to follow liquid level changes in the tank.
In one aspect the valve has an upper dome structure, a lower plug, and a trapped air pocket between the dome structure and plug. In an alternative structure the valve has an upper dome structure mounted on the float to create a trapped air pocket there between, and the upper dome structure is not integral with the portion of the float upon which it is mounted. In this latter embodiment the float can have an integral upwardly extending hub upon which the dome structure is mounted with an interference fit.
Most preferably at least a part of an upper portion of the head is a moldable flexible plastic such as polyethylene having a density of less than 1 grams/cubic centimeter (xe2x80x9cg/cm3xe2x80x9d), where at least a portion of the head has a wall thickness of less than 0.05 centimeter (xe2x80x9ccmxe2x80x9d).
The invention provides a way of improving the anti-leakage capabilities of dispensers of this type. The trapped air pocket permits some flexibility of the valve head when a thin walled plastic (a degradation-resistant material) is used, but nevertheless sufficiently supports the head such that the head will not permanently deform.
The valve head can be molded in two parts which are then combined to create a trapped air pocket. Alternatively, other ways of forming the trapped air pocket can be used (albeit these may be more expensive to implement on a commercial scale).
The net result is a dispenser with a very low rate of uncontrolled leakage. Importantly, this advantage is achieved inexpensively, and can be maintained over long term use.